Mushrooms, especially Agaricus bisporus and other Agaricus spp., are cultivated using compost (substrate) and a casing material which covers the compost. The casing material is used as a water absorbent layer, and is normally a peat/lime mixture.
In the UK and Ireland, about 0.5 million cubic meters of casing material are used annually. The other main mushroom producing countries in western Europe are Holland and France, both of which import peat and use an estimated 2 million cubic meters of casing materials. Globally, in excess of 15 million cubic meters of casing materials are used.
The amount of peat used in mushroom cultivation and other applications has given rise to considerable environmental concern. There has therefore been a considerable amount of research into the use of different materials for mushroom casing, including an extensive amount of work examining peat alternatives.
For example, WO 98/11771 and U.S. Pat. No. 6,205,703 disclose casing material for stacks and sitting-out areas in mushroom culture comprising 50-80 vol. % filter cake derived from wastes from paper manufacture, and 20-50 vol. % aggregates selected from peat, vegetable fibres, ground limestone, marl and molasses. JP-A-11/299347 discloses a culture substrate (i.e. compost substitute) for mushroom species that do not require a casing layer, based on powder derived from blast-furnace slag and/or steelmaking slag.
CN-A-1052766 discloses a material for covering mushrooms which includes, among other ingredients, coal industry wastes. These coal wastes may be cinder wastes produced from burning coal, or coal slag (ie a mixture of coal, soil and stones unsuitable for burning). The particle size of the wastes is not disclosed.
The alternative materials used in the prior art have generally given inferior mushroom yield results compared to peat-based casing. It is therefore an object of the present invention to provide a casing material capable of providing a partial or complete alternative to peat, while producing a mushroom yield at least equivalent to peat-based casing.